The 17-year-old defender completed a deadline day switch from Servette.
Kevin Mbabu: "I've always wanted to play for a big club and I have my chance with Newcastle United. I'm delighted by the move.
"I want to finish my development here and then try to join the first team.
"The speed and pace in this country is at another level. I know I will have to work hard to achieve the level here because there are some top players here.
"But I already feel at home and the club have made me feel very welcome here already."
Reserve team coach Willie Donachie: "Kevin is a very good prospect. He's still just 17 and has a lot to do. If he keeps working hard he could have a great future in the game."
Source: Newcastle United Mad